The present invention is generally related to solenoid valves having a single stator and a plurality of axially oriented armatures and more specifically to a vapor control valve which controls the rate at which hydrocarbons, stored in a canister, are permitted to re-enter the intake manifold of an engine. Prior evaporative emission systems have not been able to allow the transfer of vapors from the tank to the canister during refueling and then seal up this passageway after a pre-determined time interval. Doing this will eliminate fuel expulsion on cap removal and at the same time maintain evaporative emissions within acceptable limits.
As part of the vapor emission control system of an automotive engine a carbon canister is utilized to absorb the hydrocarbon (gas) vapors within the fuel tank thereby permitting same from reaching the atmosphere and to thereafter, once the engine is started, return at a predetermined rate such hydrocarbons to the intake manifold of the engine where these hydrocarbons are combusted.
An advantage of the present invention is to incorporate within a single device means for controlling the fuel tank pressure as well as the rate at which the engine purges the vapors stored in the carbon canister.
The present invention replaces the plurality of such valves which find use in present day automotive systems. The present invention offers improved emissions performance while at the same time reduces the risk of fuel "spit back" which can occur under certain conditions when refueling.
Fuel "spit-back" refers to the expulsion from the fuel tank filler neck of droplets of fuel. It can occur either on fuel cap removal or during the process of refueling. In either case, it usually only occurs when the fuel tank is close to being full.
Accordingly, the invention comprises a vapor control valve and system for controlling fuel take pressure and for purging hydrocarbons from a storage canister comprising a single electrical coil, responsive to control signals, wound about a carrier or bobbin including a central passage therein divided into first and second axially aligned portions; a first piston slidable received within the central passage at the first portion; a second piston slidably received within the central passage at the first portion; a first valve seat for receiving the first piston; a second valve seat for receiving the second piston, a first spring for biasing the first piston into the first valve seat; and a second spring for biasing the second piston into the second valve seat, wherein the spring constant of the first spring is less than the spring constant of the second spring.